Process of manufacturing filters



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United States Patent 3,026,226 PROCESS OF MANUFACTURING FILTERS George P. Touey and Robert C. Mumpower 11, Kingsport, Tenn., assignors to Eastman Kodak Company, Rochester, N .Y., a corporation of New Jersey No Drawing. Filed Dec. 9, 1957, Ser. No. 701,310 9 Claims. (Cl. 156-180) This invention relates to improved filters. More particularly this invention concerns tobacco smoke filters comprised of continuous synthetic filaments, which filaments have a special additive securely bonded to the surface thereof. Such improved filters are particularly useful for attaching as filter tips on cigarettes.

A wide variety of filters have already been described in the art. The first filters were made from crepe paper, wadding, and the like masses of fibers. Apparently by using masses or wads it was thought that the filtering efficiency might be increased because of the disoriented nature of the filter. However, such filters in many instances exhibited a high pressure drop. In the manufacture of such filters it was necessary to out or die a section of material from a fibrous batt or sheet. The piece of filter material thus cut was usually of a square or rectangular configuration rather than round; hence, would not lend itself readily to attachment to round cigarettes.

More recently certain continuous parallel cellulose ester filaments have been described for filter manufacturing purposes and have obtained wide-spread acceptance. Such continuous filaments have merit in that they work very well in present-day high-speed filter-making machinery. However, attempts have been made to try and improve such filament type filters by applying addi tives thereto. It has been suggested in the art that certain types of additives may be attached to the filaments or filters by creating a static charge on such filaments and using the electrical charge to cause the additives to be attracted to and bonded to the filaments. Also, various other methods and apparatuses have been suggested for use in attempting to apply additives to filters.

However, in general with respect to such prior art filtersthe additives may not be very strongly bonded to the fibers. Consequently such additives may tend to dust out of the filters. This is particularly the situation which exists with respect to prior art filters where in the manufacture of the filter it has been attempted to obtain the bonding of the additive primarily by physical forces, entrapment, or the like, when the amount of the additive is, for example, in excess of 10% of the Weight of the fibers. In the instance of cigarette filters any additive which becomes loose may get in the smokers mouth or on his lips and otherwise may be objectionable.

In addition, prior art procedures for applying additives have in many instances required dusting booths or other special equipment which adds to the cost of filter manufacture. For example, with respect to dusting booths, such dusting booths are preferably constructed with an explosion vent or top and with other safety devices in view of the possible hazard that may accompany the use and handling of dust-like materials. There are also other types of problems which have been encountered when proceeding with the application of certain additives in accordance with prior art.

It is believed apparent, therefore, that the development of an improved method, apparatus and product, where- ICC? in certain efficient additives may be applied to filament filters represents a highly desirable result. After extended investigation we have discovered an improved method whereby filter filaments may be more simply produced and which filament filters carry on the surfaces of the filaments additive materials not only in relatively large quantities but firmly bonded to the filaments.

This invention has for one object to provide an improved procedure for applying additive material to filament filters whereby the material is firmly bonded to the surface of the filaments. Another object is to provide a method whereby relatively large amounts of additives may be incorporated on and into the surface of filaments which are employed in the manufacture of filters. Still another object is to provide a method by which additives are attached to the surface of the filaments in a dispersed, divided form yet are strongly bonded to the filaments. Still another object is to provide an improved filament type of filter wherein the filaments have on their surfaces a particular type of roughness. Another object is to provide a filter made up of continuous filaments wherein the quantity of material on the surfaces of the filaments as aforesaid is not only firmly bonded but is a relatively larger quantity than heretofore possible in the prior art. Still another object is to provide a filter of the type indicated wherein the filaments making up the filter carry a wide variety of solid materials on their surface. Other objects will appear hereinafter.

As already indicated above, prior art procedures have involved the application of particle materials to the surface of filaments which are to be used in making filters. Such prior art procedure has, for example, relied on the electro-static attraction for causing adherence. Accordingly, in the prior art in many instances it has not been possible to apply more than 10% additive or to even obtain suificiently strong adherence of the additives even though small amounts were utilized. In other words, in the prior art in many instances there has been tendency for the additives on the filaments to become dislodged and to sift out of the filter when the filter has been used even in a normal manner.

In the more general aspects of our invention we have found that certain normally solid additive materials may be converted to a molten state prior to use as an additive. This conversion to a molten condition is preferably carried out in combination with a suitable plasticizer. Then the molten materials comprising the molten additive and plasticizer are incorporated on the filament filter. Upon deposit of the molten materials (liquid) on the filaments the plasticizer is absorbed by the filaments. The aforesaid normally solid material upon cooling deposits on the surface of the filaments in the shape of fine particles thereby permitting the production of nodes and ridges or the like on the surface of the filaments. Such particles deposited in the form of nodes and ridges as just mentioned are strongly bonded to the filaments so that the particles may not be dislodged from the filaments during the normal handling of the filaments in the making of filters or the subsequent handling and use of the filters. This is the situation, even though substantial amounts of the particles are thus applied to the filaments. In other words, even when the filaments contain an amount of the additive greatly in excess of 10% by weight of the filament, such particles applied by the process of the present invention do not sift or powder out of the filter.

In considering our invention in further detail the description which follows will be generally grouped under three headings, having reference to the solid type of additive which is applied to the filaments by the present invention. The three groups are fatty acid esters, fatty acids, and fatty alcohols.

Considering in detail first the use of high molecular weight fatty acid esters, the product we prefer would be a fatty acid ester which is solid at room temperature but a liquid when warmed, for example, within; the range 50100 C. The fatty acid ester preferably is one which is completely miscible with any particular plasticizer used in conjunction therewith, said miscibility being in all proportions when the fatty acid ester is in a melted state. The fattyacid ester preferably is one which is substantially insoluble in the particular plasticizer at room temperatures. The high-molecular-weight acid esters of glycerol, ethylene glycol, propylene glycol, polyethylene glycol and polypropylene glycol, which have melting points above 35 and below 100 C., are suitable for this purpose. So also are the acetylated monoglycerides with melting points within this range. In the table below there are listed several of these compounds which are quite satisfactory, being soluble in cellulose acetate plasticizers when warmed but insoluble in the plasticizers when the solutions are cooled back to room temperature.

Compound: Melting point C.) Glycerol monostearate 57-61 Diethylene glycol stearate 5459 The preferred compounds of this group are the mono stearates of glycerol and Propylene glycol, the acetylated monoglyceride and the hydrogenated castor oils since these compounds are recommended for incorporation into foods and food containers.

The cellulose acetate plasticizers which man be used as hot solvents for spraying these esters onto the cellulose acetate two are selected from those plasticizers which have been found tobe satisfactory for bonding the compressed tow into a firm or rigid filter rod. Suitable plasticizers are as follows: Glycerol diand triacetates, glycerol diand tripropionates, di-(methoxyethyl) phthalate, ethyl phthalyl methyl glycollate, triethyl citrate and miktures of these plasticizers.

The preferred plasticizers are glycerol triacetate or a mixture of glycerol diacetate and glycerol triacetate. These plasticizers are capable of bonding the cellulose acetate filaments into a firm rod without the application of heat. 7

In order to obtain a sufiicient amount of the highmolecular-weight fatty acid ester on the surface of the filaments to produce a firm and effective filter, it has been found that the solid ester should be dissolved in the plasticizer to an amount not less than 25% and not more than 80%. The preferred amount of dissolved highm olecular-weight fatty acid ester in the plasticizer is 40-70%. The amount of total additive solution (plasticizer and dissolved ester) that should be sprayed on the two will depend on the type of continuous filaments (number and'size of filaments and degree of crimps given to the filaments) employed and the ratio of plasticizer to dissolve ester in the spray solution. In order to obtain sufficient amount of the solid ester particle deposited on a filament bundle, it is usually desirable to add from 20 to 60% of a 50/50 plasticizer-glycerol (or glycol) ester to the filaments before they are converted to a filter plug. This will give from 15 to 30% solid additive on the filaments. In general, it has been found that at least 10% of the solid ester particles should be distributed on the surface of the filaments before an appreciable improvement in the filters efficiency can be realized to the fullest extent.

The size of the solid ester particles which deposit on the tow is governed mainly by the openings on the spray gun. It has been found that with a conventional paint spraying gun particle sizes between 5 and 30 microns are easily obtained. However, with fine spray attachments it is possible to produce sprays with particle sizes from 0.5 to 10 microns. As a general rule, it is more desirable to use a spraying device which maintains the particle size below 20 microns. In this Way an easy drawing filter is assured since relatively large particles deposited on the filaments have a tendency to increase the pressure drop of the filter to an appreciable degree.

In the following examples and descriptions are set forth several of the preferred embodiments using the first groups of solids which are included merely for the purpose of illustration and not as a limitation thereof.

EXAMPLE I A S-foot length of tow of cellulose acetate yarn, containing 10,000 filaments of 8 denier per filament and having an average of 9 crimps per inch along its entire length, was spread out to a width of 12 inches. While in this spread out condition, the tow was sprayed on both sides with a solution consisting of equal parts by weight of glycerol monostearate and glycerol triacetate maintained (within the spray gun) at a temperature of 70 C. This solution was prepared by adding the solid glycerol monosterate to the liquid glycerol triacetate and heating the mixture to 60-70 C. As the glycerol monostearate melted, it dissolved in the glycerol triacetate giving a homogeneous solution.

After the tow was so treated, the combination consisting of 64% cellulose acetate filaments, 18% glycerol monostearate and 18% glycerol triacetate (plasticizer) was pulled back into a compact bundle or cord and fed into a cigarette filter plug making machine which paper wrapped it and cut it into the filter rods 90 mm. in length and 25.5 mm. in circumference. After being stored for 20 minutes at 28 C. (82.4 F.) the rods were quite rigid. Some of the rods were opened and observed under the microscope. This revealed that substantially all of the filaments had a rough and irregular surface due to the fact that the glycerol monostearate had deposited on the tow as a fine powder which was firmly bound toit through the plasticizer. Several of the rods were cut into filter tips, 15 mm. in length. These tips were attached to 10 cigarettes (Standard Brand A) mm. in length which had been shortened by 15 mm. to compensate for the length of the filter. These 10 iiitered cigarettes were smoked to butt lengths of 35 mm. on a smoking machine similar in design and operation to the smoking machine described by J. A. Bradford, W. R. l-larlan, and H. R. Hanmer in Industrial and Eng. Chemlstry, vol. 28, pp. 836-839, 1936. The smoke which passed through the cigarettes was collected and analyzed for nicotine and tar content. The results are shown in Table 1.

Control filters containing no additive and control filters containing 18% glycerol triacetate' (plasticizer) alone were prepared from the same crimped tow described above. These filterswere attached to the same Brand A cigarettes shortened by 15 mm. Ten of the cigarettes with the filters containing no plasticizerand ten of the cigarettes with the filters containing 18% glycerol triacetate were also smoked to butt lengths of 35 mm. by means of the smoking machine. The smoke which passed through the cigarettes was collected and analyzed for nicotine and tar content. The results are shown in Table 1.

Ten unfiltered king size cigarettes (Brand A) which were not shortened by 15 mmaweresmoked to'butt lengths of 35 mm. by means of the smoking machine. The smoke which passed through the cigarettes was collected and analyzed for nicotine and the content. The results obtained are shown in Table 1.

25.6 mm. in circumference.

- manner.

Table 1 MILLIGRAMS OF NIOOTINE AND TAR OBTAINED FROM SMOKING FILTERED AND UNFILTERED OIGARETTES Av. Mg. Percent Percent Pressure Mg. Tar-s, Nicotine, Nicotine Tar Re- Drop, Ciga- 10 Ciga- Reduction duction In. rettes rettes Due to Due to Filter Filter Cigarettes without filters (85 mm. total length) 3. 1 170 29 Cigarettes with acetate filters (85 mm. total length)- 3. 6 150 25 11. 8 13 8 Cigarettes with acetate filters containing 18% glycerol triacetate (85 mm. total length) 3. 5 153 26 10.0 10.4 Cigarettes with acetate filters containing 18% glycerol triacetate and 18% glycerol monostegrate (85 mm. total 1 length) 3.9 110 20 35.3 31.0

The nicotine and tar reduction values shown in Table 1 show that the filter with the liquid plasticizer (bonding agent) removed slightly less nicotine and tar than the filter without any additive. However, when the glycerol monostearate dissolved in the plasticizer was added to the tow, the efilciency of the filter was increased appreciably. This increase in filtering efficiency was obtained without a substantial increase in the pressure drop of the cigarette.

EXAMPLE II A 5-foot length of cellulose acetate yarn tow containing 14,000 filaments of 5 denier per filament and having an average of 9 crimps per inch along its entire length was spread out to a width of 12 inches. While in this spread out condition the tow was sprayed on both sides with a solution consisting of 70% hydrogenated castor oil and 30% glycerol triacetate by weight. During the spraying operation, the solution was maintained at 85 C. within the spray gun. After the tow was so treated the combination consisting of 70% cellulose acetate fibers, 21% hydrogenated castor oil, and 9% glycerol triacetate was pulled back into a compact bundle or cord and fed into the cigarette filter plug making machine which paper wrapped it and cut it into filter rods 90 mm. in length and After being stored for 20 minutes at approximately 30 C., the rods were rigid and could be readily cut into filter tip lengths of 15 mm. These tips were attached to 10 cigarettes (Brand A) 85 mm. in length which had been shortened by 15 mm. and the cigarettes were smoked to butt lengths of 35 mm. on the automatic smoking machine. passed through the cigarettes was collected and analyzed for nicotine and tar content. 19 mg. of nicotine were found in the smoke from the 10 cigarettes. When these values are compared with those obtained from the unfiltered cigarette (Table 1), it is found that the filter removes 40% more tar and 34.6% more nicotine than the 15 mm. length of tobacco it replaced. The average pressure drop of the filtered cigarettes was 4.0 inches of water. Control filters containing 10%, 20%, and glycerol triacet-ate, respectively, were prepared from the sme crimped tow in a similar The filters containing 10% plasticizer removed 20% more nicotine and 10% more tars than the 15 mm. tip of tobacco they replaced. The filters containing 20% plasticizer removed 18% more tars and 18% more nicotine while the filters containing 30% plasticizer removed only 15% more tars and 17% more nicotine. The average pressure drops for these three sets of filtered cigarettes ranged from 3.6 to 4.1 inches.

EXAMPLE HI A continuous tow of cellulose acetate containing 14,000 filaments of 5 denier per filament and having an avcrage of 9 crimps per inch along its entire length was The smoke which Only 102 mg. of tar and spread out to a width of 12 inches. While in this spread condition the tow was pulled through a spray booth wherein it was sprayed on both sides with glycerol triacetate plasticizer (unheated). After this treatment the spread out tow was then pulled through another booth wherein it was sprayed on both sides with glycerol monostear-ate (M.P. 5761 C.) maintained within the spray gun at C. As the liquid ester emerged from the gun it formed a mist of fine solid particles which were uniformly distributed over the surface of the tow.

After the tow was so treated the combination consisting of 67% cellulose acetate fibers, 17% glycerol monostearate and 16% glycerol triacetate plasticizer was pulled back into a compact bundle or cord and fed into the filter machine which paper wrapped it and cut it into rods mm. in length and 25.6 mm. in circumference. After being stored for 20 minutes at room temperature the rigid rods were cut into tips 15 mm. in length. These tips were attached to 10 cigarettes (Brand A) which were originally 85 mm. in length but which were shortened to 70 mm. to compensate for the length of the filter. The filtered cigarettes were smoked to butt lengths of 35 mm. on the automatic smoking machine. The smoke which passed through the cigarettes was collected and analyzed for nicotine and tar content. Only 99 mg. of tar and 16 mg. of nicotine were found in the smoke from the 10 cigarettes. When these values are compared With those obtained from the unfiltered cigarettes (Table 1) it is found that the filter removed 42% more tar and 45% more nicotine than the 15 mm. length of tobacco it replaced. The average pressure drop of the filtered cigarette was 4. 1 inches.

In accordance with the next description we now describe our invention as carried out with a high-molecularweight fatty acid material which is normally solid at room temperature.

The high-molecular-weight fatty acids which have melting points above 35 and below 100 C. are quite suitable for this purpose. They can be represented by the empirical formulas C I-1 0 and 'C H O wherein n is 10 to 24 and x is an integer from 1-5. The C H O formula represents the saturated fatty acids and the C H O represents the unsaturated fatty acids. In the tables below are listed several of these compounds which are quite satisfactory, being soluble in the cellu lose acetate bonding plasticizers when warmed but insoluble in the plasticizers when the solutions are cooled.

Saturated Fatty Acids (OnHznO2) Name Melting Formula P int OUEMCOOH 43-44 C H27COOH 53-54 C;5H31COOH 62-63 CnHasCOOH 68-70 gun.

Unsaturated Fatty Acids (CnH2n2x 02) Name Melting Formula Point erncic OH3(CH2)7CH= CH (CHnnOOOH 35 ela1d1c CH3(CH2)7CH= H(CH)1OOOH 51-52 elaceostearic OH3 CH2 3OH=CHCH=OHCH=CH(CH2)7000H 49-50 angelic OH3CH=C(CH3)COOH 45 In addition, the fatty acids may contain substituent groupings (hydroxyl, carbonyl, chloro, etc.). However, if the substituent groups on the fatty acid render the acid insoluble in the plasticizer at the deisred temperature range of 35-100 C. or if they radically alter its melting point such substituted fatty acids are not satisfactory. v

The preferred fatty acids are the straight chain, naturally occurring saturated fatty acids such as myristic, palrnitic and stearic acid since these acids are inexpensive, completely nontoxic, and have little or no odor.

The plasticizers which can be used as hot solvents for spraying these acid additives onto the filaments are selected from those plasticizers which have been found to be satisfactory for bonding the compressed filaments into a firm or rigid filter rod. Suitable plasticizers are as follows: glycerol diand triacetates, glycerol diand tripropionates, dHmethoxyethyl) phthalate, ethyl phthalyl methyl glycollate, triethyl citrate and mixtures of these plasticizers.

The preferred plasticizers are glycerol triacetate or a mixture of glycerol diacetate and glycerol triacetate. These plasticizers are capable of bonding the filament bundle into a firm rod without the application of heat.

In order to obtain a sufficient amountof the highmolecular-weight fatty acid on the surface ofthe filaments to produce a firm and effective filter, it has been found that the solid acids should be dissolved in the plasticizer to an amount not less than 25% and not more than 80%. The preferred amount of dissolved high-molecular-weight fatty acid in the plasticizer is 40*70%. The amount of total additive solution (plasticizer and dissolved acid) that should be sprayed on the filaments will depend on the type of filaments (number and size of filaments) and the degree of crimps given to the bundle employed and the ratio of plasticizer to dissolved acid in the spray solution. In order to obtain sufiicient amount of the solid acid particles deposited .on a tow, it is usually desirable to add from 20 to 60% of a 50/50 plasticizer-fatty acid solution to the filament bundle before it is converted to a filter plug. This will give from 15 to 30% solid additive on the filaments. In general, it has been found that at least 10% of the solid acid particles must be distributed on the surface of the filaments before the desired improvement in the filters efiiciency can be realized.

The size of the solid acid particles which deposit on the tow is governed mainly by the openings on the spray It has'been found that with a conventional paint spraying gun particle sizes between 5 and 30 microns are easily obtained. However, with fine spray attachments it is possible to produce spray with particle sizes from 0.5 to microns. As a general rule it is more desirable to use a spraying device which maintains the particle size below microns. In this way an easy drawing filter is assured since relatively large particles deposited on the fibers have a tendency to increase the pressure drop of the filter to'an appreciable degree.

In the following examples and descriptions are set forth several of the preferred embodiments of this species of our invention.

EXAMPLE IV A 5-foot length of tow of cellulose acetate yarn, containing 10,000 filaments of 8 denier per filament and having an average of 9 crimps per inch along its entire length, was spread out to a width of 12 inches. While in this spread out condition, the tow was sprayed on both sides with a solution consisting of equal parts by Weight of stearic acid and glycerol triacetate maintained (within the spray gun) at a temperature of C. This solution was prepared by adding the stearic acid to the liquid glycerol triacetate and heating the mixture to 60-70" C. As the acid melted it dissolved in the glycerol triacetate giving a homogeneous solution.

After the tow was so treated, the combination cons'isting 0f 62% cellulose acetate filaments, 19% stearic acid and 19% glycerol triacetate (plasticizer) was pulled back into a compact bundle or cord and fed into a cigarette filter plug-making machine which paper wrapped it and cut it into filter rods 90 mm. in length and 25.5 mm. in circumference. After being stored for 30 minutes at 27 C., the rods were quite rigid. Some of the rods were opened and observed under the microscope. This revealed that substantially all of the filaments had a rough and irregular surface due to the fact that the stearic acid had deposited on the filaments as, a fine powder which was firmly bound to the filaments. Several of the rods were cut into filter tips, 15 mm. in length. These tips were attached to 10 cigarettes (Standard Brand A) mm. in length which had been shortened by 15 mm. to compensate for the length of the filter. These 10 filtered cigarettes were smoked to butt lengths of 35 mm. on a smoking machine similar in design and operation to the smoking machine described by I. A. Bradford et al. in Industrial and Engineering Chemistry, vol. 28, pp. 836-839, 1936. The smoke which passed through the cigarettes was collected and analyzed for nicotine and tar content. The results are shown in Table 2.

Control filters containing no additive and control filters containing 19% glycerol triacetate (plasticizer) alone were prepared from the same crimped filament starting material described above. These filters were attached to the same Brand A cigarettes shortened by 15 mm. Ten of the cigarettes with the filters containing no plasticizer and ten of the cigarettes with the filters containing 19% glycerol triacetate were also smoked to butt lengths of 35 mm. by means of the smoking machine. The smoke which passed through the cigarettes was collected and analyzed for nicotine and tar content. The results are shown in Table 2.

Ten unfiltered king size cigarettes (Brand A) which were not shortened by 15 mm. were smoked to butt lengths of 35 mm. by means of the smoking machine. The smoke which passed through the cigarettes was collected and analyzed for nicotine and tar content. The results obtained are shown in Table 2.

Table 2 AND TAR OBTAINED FROM SMOKING FILTERED AND BIILLIGRAMS OF N'IGOIINE UNFILTERED CIGARETTES Av. Mg. Percent Percent Pressure Mg. Tars, Nicotine, Tar Nicotine,

Drop, 10 Ciga- 10 Ciga- Reduc- Reduc- In. rettes rettes tion Due tion Due to Filter to Filter Cigarettes without filters (85 min. total length) 3.1 170 29 Cigarettes with acetate filters (85 mm. total length) 3. 6 150 25 11. 8 13. 8 Cigarettes with acetate filters containing 19% glycerol triacetata (85 mm. total length) 3. 156 26 8.3 10. 4 Cigarettes with acetate filters containing 19% glycerol tiiacetate and 19% stearic acid (85 mm. total length) 3. 9 106 19 37. 5 34. 5

1 Pressure drop expressed as inches of Water at an air flow rate of 17.5 nil/sec. though the cigarette.

The nicotine and tar reduction values shown in Table 2 show that the filter with the liquid plasticizer (bonding agent) removed slightly less nicotine and tar than the filter without any additive. However, when the stearic acid dissolved in the plasticizer was added to the tow, the efliciency of the filter was increased appreciably. This increase in filtering efficiency was obtained without a substantial increase in the pressure drop of the cigarette.

EXAMPLE V A 5-foot length of cellulose acetate yarn containing 14,000 filaments of 5 denier per filament and having an average of 9 crimps per inch along its entire length was spread out to a width of 12 inches. While in this spread out condition the yarn was sprayed on both sides with a solution consisting of 70% palmitic acid and 30% glycerol triacetate by weight. During the spraying operation, the solution was maintained at 80 C. within the spray gun. After the yarn was so treated the combination consisting of 70% cellulose acetate, 21% palmitic acid, and 9% glycerol triacetate was pulled back into a compact bundle or cord and fed into the cigarette filter plug-making machine which paper wrapped it and cut it into filter rods 90 mm. in length and 25.6 mm. in circumference. After being stored for 20 minutes at approximately 30 (1., the rods were rigid and could be readily cut into filter tip lengths of 15 mm. These tips were attached to cigarettes (Brand A) 85 mm. in length which had been shortened by mm. and the cigarettes were smoked to butt lengths of 35 mm. on the automatic smoking machine. The smoke which passed through the cigarettes was collected and analyzed for nicotine and tar content. Only 99 mg. of tar and mg. of nicotine were found in the smoke from 10 cigarettes. When these values are compared with those obtained from the unfiltered cigarette (Table 2) it is found that the filter removes 42% more tar and 38% more nicotine than the 15 mm. length of tobacco it replaced. The average pressure drop of the filtered cigarettes was 4.0 inches of water.

Control filters containing 10%, 20%, and glycerol triacetate, respectively, were prepared from the same crimped yarn in a similar manner. The filters containing 10% plasticizer removed 20% more nicotine and 19% more tars than the 15 mm. tip of tobacco they replaced. The filters containing 20% plasticizer removed 18% more tars and 18% more nicotine while the filters containing 30% plasticizer removed only 15% more tars and 17% more nicotine. The average pressure drops for these three sets of filtered cigarettes ranged from 3.6 to 4.1 inches.

EXAMPLE VI A continuous tow of cellulose acetate containing 14,000 filaments of 5 denier per filament and having an average of 9 crimps per inch along its entire length was spread out to a width of 12 inches. While in this spread condition the tow was pulled through a spray booth wherein it was sprayed on both sides with glycerol triacctate plasticizer (unheated). After this treatment the spread out filaments were then pulled through another booth wherein it was sprayed on both sides with stearic acid (M.P. 69 C.) maintained within the spray gun at a temperature of C. As the liquid acid emerged from the gun it formed a mist of fine solid particles which were uniformly distributed over the surface of the tow.

After the tow was so treated the combination consisting of 69% cellulose acetate filaments, 18% stearic acid, and 13% glycerol triacctate plasticizer was pulled back into a compact bundle or cord and fed into the filter machine which paper wrapped it and cut it into rods mm. in length and 25.6 mm. in circumference. After being stored for 20 minutes at room temperature the rigid rods were cut into tips 15 mm. in length. These tips were attached to 10 cigarettes (Brand A) which were originally 85 mm. in length but which were shortened to 70 mm. to compensate for the length of the filter. The filtered cigarettes were smoked to butt lengths 35 mm. on the automatic smoking machine. The smoke which passed through the cigarettes was collected and analyzed for nicotine and tar content. Only 103 mg. of tar and 19 mg. of nicotine were found in the smoke from the 10 cigarettes. When these values are compared with those obtained from the unfiltered cigarettes (Table 2) it is found that the filter removed 39% more tar and 35% more nicotine than the 15 mm. length of tobacco it replaced. The average pressure drop of the filtered cigarettes was 3.9 inches.

In accordance with the next description we now describe our invention as carried out with a high-molecularweight fatty alcohol.

In order to produce this desired effect in this invention, the dissolved alcohol should be a solid at room temperature but a liquid when warmed (SO- C.). It preferably is completely miscible with the plasticizer in all proportions when it is in the melted state and is substantially insoluble in the plasticizer at room temperatures, that is below 400 C.

Although any alcohol having a melting point above 35 and below 100 C. is in many instances satisfactory for the operation of this invention, it is preferred to use those alcohols which are known to be nontoxic and which can be obtained from natural sources. The fatty alcohols which can be derived from their corresponding naturally occurring esters, are ideally suited for this purpose. Stearyl alcohol (octadecanol) and cetyl alcohol (hexadecanol) are examples of such alcohols. Cetyl alcohol, CH (CH OH melts at 49-50 C. and stearyl alcohol CH (CH ';OH melts at 5860 C. Both alcohols are soluble in the heated plasticizers or bonding agents for synthetic filaments but substantially insoluble in the plasticizers below 40 C.

In addition, the fatty alcohols may contain substituent groupings (hydroxyl, carbonyl, chloro, etc.). However, the substituent group should not alter its melting point or its solubility characteristics to such an extent that these properties would bar its use within the scope of this invention. In other words, the substituted alcohol would be a filter plug. .tive on the filament bundle.

' spray gun.

seasons 1 1 a solid at 40 C. or above and be insoluble in the plasticizer at temperatures below 40 C.

The cellulose acetate plasticizers which can be used as hot solvents for spraying the alcohols on the cellulose acetate tow are selected from those plasticizers which have been found to be satisfactory for bonding the compressed tow into a firm or rigid filter rod, and are as al-' degree of crimps given to the filaments) employed and the ratio'of plasticizer to alcohol in the spray solution. In order to obtain suflicient amount of the alcohol particles deposited on a bundle of filaments, it is usually necessary to aid from 20 to 60% of a 50/50 plasticizeralcohol mixture to the filaments before it is converted to This will give from 15 to 30% solid addi- In general, it has been found that at least 10% of the solid alcohol particles must be distributed on the surface of the filaments before an appreciable improvement in the filters elficiency can be realized.

The size of the alcohol particles which deposit on the filaments is governed mainly'by the openings on the It has been found that with a conventional paint spraying gun, particle sizes between 5 and 30 microns may be obtained. However, with fine spray attachments it is possible to produce sprays with particle sizes from 0.5 to microns. As a general rule, it is more desirable to use a spraying device which maintains the particle size below microns. In this way an easy drawing filter is assured.

In the next examples and descriptions are set forth several of the preferred embodiments of this invention treated, the combination consisting of 68% cellulose acetate, 16% stearyl alcohol and 16% glycerol triacetate (plasticizer) was pulled back into a compact bundle or cord and fed into a cigarette filter plug-making machine which paper wrapped it and cut it into filter rods 90 mm. in length and 25.5 mm. in circumference. After being stored for 30 minutes at 27 C., the rods were quite rigid. Some of the rods were opened and observed under the microscope. This revealed that substantially all of the fibers had a rough and irregular surface due to the fact that the stearyl alcohol had deposited on the filaments as a fine powder, which powder was firmly bound to it through the plasticizer. Several of the rods were cut into filter tips, 15 mm. in length. These tips were attached to 10 cigarettes (Standardv Brand A), 85 mm. in length which had been shortened by 15 mm. to compensate for the length of the filter. These 10 filtered cigarettes were smoked to butt lengths of 35mm. on a smoking machine similar in design and operation to the smoking machine described by l. A. Bradford et al. in Industrial and Engineering Chemistry, 28, 836839, 1936. The smoke which passed through the. cigarettes was collected and analyzed for nicotine andtar content. The results are shown in Table 3.

Control filters containing no additive and control filters containing 19% glycerol triacetate (plasticizer) alone were prepared from the same crimped filaments described above. These filters were attached to the some Brand A cigarettes shortened by '15 mm. Ten of the cigarettes with the filters containing no plasticizer and ten of the cigarettes with the filters containing 19% glycerol triacetate plasticizer were also smoked to butt lengths of 35 mm. by means of the smoking machine. The smoke which passed through the cigarettes was collected and analyzed for nicotine and tar content. The results are shown in Table 3.

Ten unfiltered king size cigarettes (Brand A) which were not shortened by I5 mm. were smoked to butt lengths of 35 mm. by means of the smoking machine. The smoke which passed through the cigarettes was collected and analyzed for nicotine and tar content. The results obtained arelshown in Table 3.

Table 3 MILLIGRALNIS OF NICO'IINE AND TAR OBTAINED FROM SMOKING FILTERED AND UNFILTERED CIGARETTES.

Av. Mg. Percent Percent Pressure Mg. Tars, Nicotine, Tar Re- Nicotine Drop, 10 Ciga- 10 Oigaduction Reduc- In. 'rettes rettes Due to tlon Due Filter to Filter Cigarettes without filters (85 mm. total length) 3. 1 170 29 Cigarettes with acetate filters (85 mm. total length) 3. 6 150 25 11. 8 13. 8 Cigarettes with acetate filters containing 19% gylcerol triacetate (85 mm. total length) 3. 5 156 26 8. 3 10.4 Cigarettes with acetate filters containing 16% glycerol triacetate and 16% stearyl alcohol (85 mm. total length)- 4; 0 112 20- 34. 0 31. 0

Pressure drop expressed as inches of water at an air flow rate of 17. 5 ml./sec. through the cigarette.

pertaining to the use of alcohols of the class described above.

EXAMPLE VII A five-foot length of cellulose acetate continuous filament yarn, containing 10,000 filaments of 8 denier per filament and having an average of 9 crimps per inch along its entire length, was spread out to a width of 12 inches. While in this spread out condition, the tow was sprayed on both sides with a solution consisting of equal parts by weight of stearyl alcohol and glycerol "triacetate maintained (within the spray gun) at a temperature of 70C. This solution was prepared by adding the'stearyl alcohol to the liquid glycerol triacetate and heating the mixture to -70" C. As the alcohol melted it dissolved in the glycerol triacetate giving a homogeneous EXAMPLE VIII A five-foot length of cellulose acetate continuous filament yarn containing 14,000 filaments of 5 denier per filament and having an average of 9 crimps per inch along its entire length was spread out to a width of 12 inches. While in this spread out condition, the yarn was sprayed on both sides with a solution consisting of 70% cetyl solution. After the continuous filament yarn was so alcohol and 30% glycerol triacetate by weight. During was pulled back into a compact bundle or cord and fed into the cigarette filter plug making machine which paper wrapped it and cut it into filter rods 90 mm. in length and 25.6 min. in circumference. After being stored for 20 minutes at approximately 30 C., the rods were rigid and could be readily cut into filter tip lengths of 15 mm. These tips were attached to cigarettes (Brand A) 85 mm. in length which had been shortened by mm. and the cigarettes were smoked to butt lengths of 35 mm. on the automatic smoking machine. The smoke which passed through the cigarettes was collected and analyzed for nicotine and tar content. Only 106 mg. of tar and mg. of nicotine were found in the smoke from the 10 cigarettes. When these values are compared with those obtained from the unfiltered cigarette (Table 3) it is found that the filter removes 38% more tar and 31% more nicotine than the 15 mm. length of tobacco it replaced. The average pressure drop of the filtered cigarettes was 4.1 inches of water.

Control filters containing 10%, 20%, and 30% glycerol triacetate, respectively, were prepared from the same crimped yarn in a similar manner. The filters containing 10% plasticizer removed 20% more nicotine and 19% more tars than the 15 mm. tip of tobacco they replaced. The filters containing 20% plasticizer removed 18% more tars and 18% more nicotine while the filters containing 30% plasticizer removed only 15% more tars and 17% more nicotine. The average pressure drops for these sets of filtered cigarettes ranged from 3.6 to 4.1

inches.

While in the above examples we have shown various combinations of solid materials with various plasticizers, which combinations may be applied to filaments, and the resultant filaments carrying particles of solids are formed into improved filters, there are other combinations which also give good results. For example, we have found a spray composition which may be made up of about 55% triacetin plasticizer and 45% of the molten solids. The molten solids are comprised of 80% Myverol and 20% Myvacet. Myverol is a distilled monoester, such as glycerol monostearate. Myvacet is a hydrogenated, acetylated monoglyceride. By using the combination of Myverol and Myvacet the former appears to function to some extent as a binder for more strongly bonding the Myverol to the filaments.

In the above examples and descriptions, the percentages referred to are by weight. Of the several examples set forth above we prefer the procedure wherein the solid and the plasticizer are premixed and premelted as this is advantageous in the saving of equipment and operational steps. Of the various solids we prefer the esters and alcohols. Of the esters we prefer glycerol monostearate, and hydrogenated castor oil. Of the alcohols we prefer stearyl alcohol.

In carrying out our process we prefer to use apparatus that is suitably jacketed or insulated for heat supply and retention. That is, the spray booth wherein the spreadout filaments are sprayed with the plasticizer-solid composition would preferably have all of the booth surfaces heated above the melting point of the spray composition. There would, of course, be heated melt pots for the plasticizer and solid additive. The conduits, sprays and pumps handling the hot solution of the additive and plasticizer are suitably jacketed to retain the heat. By such construction any spray droplets not attaching to the spreadout filaments will not solidify onto the apparatus but are still maintained in a fluid condition. Such fluid may be withdrawn from the lower part of the spray booth and recycled.

As the filaments which have been sprayed leave the spray booth suitable cooling devices may be mounted adjacent the exit so that the sprayed filaments may be cooled thereby causing the sprayed on particles to solidify in the form of nodes or ridges on the surface of the filaments. The various rolls and the like parts which are positioned adjacent the exit for pulling the sprayed filaments through the spray booth are fitted with suitable blades and a collection means so that any solid which deposits 'on such rolls may be scraped olf into the collection means and returned to the melt pots.

It is believed apparent from the foregoing description that we have provided relatively simple and economical procedure for incorporating substantial amounts of additive onto the filament filters. Not only is it possible to satisfactorily apply somewhat larger amounts of additive to the surface of the filaments than heretofore possible by some of the prior art procedures but by the present invention it is possible to cause such additives to be much more firmly attached to the filaments. Since the present invention does not involve the use of dust, there is not only a possible saving in equipment costs but any danger due to the possibility of electrical discharge setting off a dust explosion is avoided.

The filter products resulting from our invention as shown by the data in the several tables appearing above comprise products which exhibit improved filtering efiiciency over similar type products heretofore produced in the art. Other advantages and benefits will be apparent to those skilled in the art.

We claim:

1. The process of manufacturing filter elements which comprises spreading out at least 10,000 continuous cellulose acetate filaments, spraying the spread-out filaments with a fiowable liquid composition of a temperature greater than 50 C., said liquid composition consisting essentially of a non-toxic plasticizer for said cellulose acetate and 25-80% of a high-molecular-weight nontoxic aliphatic compound from the group consisting of aliphatic esters, acids, and alcohols which we normally solid at room temperature but which are liquids at temperatures between 40 C. C. and are miscible with said plasticizer at a temperature between 40 C. and 100 C., the spraying being accomplished by a procedure wherein the liquid composition is sprayed on the surface of the filaments at a temperature between 40 C. and 100 C. and solidifies with a particle size of 53 microns, the plasticizer being absorbed by the filaments and the aliphatic compound depositing on and being firmly bonded to the surface of the filaments as dispersed particles whereby the filaments have nodes and ridges thereon, compacting the sprayed filaments into a bundle, wrapping the compacted bundle, cutting the wrapped bundle into lengths, storing said lengths at a temperature greater than 20 C. for more than 20 minutes whereby the plasticizer action on the filaments causes said lengths to assume rigidity.

2. The process of manufacturing filter elements which comprises spreading out at least 10,000 continuous cellulose acetate filaments, spraying the spread-out filaments with a. flowable liquid composition of a temperature between 40 C. and 100 C., said liquid composition consisting essentially of a non-toxic plasticizer for said cellulose acetate and 4070% of a high-molecular weight nontoxic aliphatic compound from the group consisting of aliphatic esters, acids, and alcohols which are normally solid at room temperature but which have melting points within the range of 40 C. to 100 C. and are miscible with said plasticizer at a temperature between 40 C. and 100 C., the spraying being accomplished by a procedure wherein the the liquid com-position is sprayed at a temperature below 100 C. and is deposited on the surface of the filaments with a particle size of less than 10 microns, the plasticizer being absorbed by the filaments and the aliphatic compound depositing on and being firmly bonded to the surface of the filaments as dispersed particles whereby the filaments have nodes and ridges thereon,

15 compacting the sprayed filaments into a bundle, wrapping the compacted bundle, cutting the wrapped bundle into lengths, storing said lengths at a temperature greater than 20 C. for more than 20 minutes whereby the plasticizer action on the filaments causes said lengths to assume rigidity.

3. The process of manufacturing filament filter elements which comprises spreading out a plurality of continuous cellulose ester filaments, applying to the spreadout filaments a fiowalble liquid composition comprised of triacetin plasticizer and a mixture of molten solids miscible with said plasticizer, the mixture of solids comprising glycerol monostearate and hydrogenated acetylated monoglyceride, forming the sprayed filaments into a filter element and subjecting the filter element to a temperature of greater than 20 C. for a period of time of the order of 2030 minutes.

4. In a process for the manufacture of filament filters, which filaments have particles on the surface of the filaments in the form of nodes and ridges firmly bonded to the filaments, the steps which comprise spreading out the filaments, applying to the spread-out filaments a melted material from the group consisting of high-molecular-Weight non-toxic aliphatic esters, acids, and alcohols which are normally solid at room temperature but which will liquefy upon heating to a temperature within the range of 50100 C., said melted material being further characterized in that it is not entirely taken up by the filament whereby said application being such that the liquid high-molecular-weight materials deposit on the surface of the filaments in a particle size of less than 30 microns.

5. The process in accordance with claim 4 wherein the application of the molten materials to the filaments is car- 16 ried out in a heated environment whereby molten material not depositing on and adhering to the surface of the filaments may be kept in'a fluid condition, withdrawn and recycled.-

6. A process in accordance with claim 1 wherein the plasticizer is from the group consisting of glycerol diand triacetates, glycerol di and tripropionates, di-(rnethoxyethyl) phthalate, ethyl phthalyl methyl glycollate, triethyl citrate and mixtures of these plasticizers.

7. A process in accordance with claim 1 wherein the plasticizer and high-molecular-weight materials are about equal proportions in the liquid being applied to the filaments and 20-60% of said liquid is applied to the spreadout filaments.

8. A process in accordance with claim 1 wherein the plasticizer is a glycerol derivative and the solid is an aliphatic stearic derivative.

9. A process in accordance with claim 1 wherein two high-molecular-weight, aliphatic compounds normally solid. at room temperature and having melting points within the range of 40 C. C. are incorporated in the plasticizer.

References Cited in the file of this patent Touey Apr. 14, 1959 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,026,226 March 20, 1962 George P. Touey et al.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, in the table, line 31, after "Diethylene glycol stearate 54-59" add the following:

Ethylene glycol monostearate "57-60 Carbowax 4000 monostearate 506O Carbowax 4000 monostearate 5457 The triglyceride of 12-hydroxy stearic acid 84 The acetylated monoglyceride from hydrogenated lard 42-44 Propylene glycol monostearate 5862 column 3, line 39, for "man" read can lines 41 and 62, for "two", each occurrence, read tow columns 5 and 6, Table I, heading to the second column, before "Av." insert an asterick; at the bottom of same table insert Pressure drop expressed as inches of water at an air flow rate of 1705 ml./sec. through the cigarette same table, headings to the fifth and sixth columns thereof should appear as shown below instead of as in the patent:

Percent Percent Tar Reduction Nicotine Due to Filter Reduction Due to Filter same Table I, last compound, for "monostegrate" read mogostearate column 10, line 55, for 400 C." read 40 C, column 14, line 45, for "5-3 read Signed and sealed this 7th day of August 1962.

(SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents 

4. IN A PROCESS FOR THE MANUFACTURE OF FILAMENT FILTERS, WHICH FILAMENTS HAVE PARTICLES ON THE SURFACE OF THE FILAMENTS IN THE FORM OF NODES AND RIDGES FIRMLY BONDED TO THE FILAMENTS, THE STEPS WHICH COMPRISES SPREADING OUT THE FILAMENTS, APPLYING TO THE SPREAD-OUT FILAMENT A MELTED MATERIAL FROM THE GROUP CONSISTING OF HIGH-MOLECULAR-WEIGHT NON-TOXIC ALIPHATIC ESTERS, ACIDS, AND ALCOHOLS WHICH ARE NORMALLY SOLID AT ROOM TEMPERATURE BUT WHICH WILL LIQUEFY UPON HEATING TO A TEMPERATURE WIHTIN THE RANGE OF 50-100*C., SAID MELTED MATERIAL BEING FURTHER CHARACTERIZED IN THAT IT IS NOT ENTIRELY TAKEN UP BY THE FILAMENT WHERBY SAID APPLICATION BEING SUCH THAT THE LIQUID HIGH-MOLECULAR-WEIGHT MATERILS DEPOSIT ON THE SURFACE OF THE FILAMENTS IN A PARTICLES SIZE OF LESS THAN 30 MICRONS. 